Filter valve



FIG. 1 is a top plan view, showing my new design.

FIG. 2 is a front view thereof.

FIG. 3 is a perspective view thereof; and,

FIG. 4 is a side view thereof.

The broken lines showing of unclaimed portions of a filter valve form no part of the claimed design. 

The ornamental design for a filter valve, as shown and described. 